arrays - 当组件 0 更改时重置 UIPickerView 第一个组件的值

Question

我不知道如何在组件 0 更改时将 PickerView 的第一个组件中使用的数组重置为组件 0(为了避免由于 indexOutOfRange 可能导致的错误)。

这是我的数据结构

let bananas = ["banana1", "banana2"]
let fruitArray = ["banana1" : ["cherry1","cherry2"], "banana2" : ["cherry1", "cherry2", "cherry3"]]


func numberOfComponents(in pickerView: UIPickerView) -> Int {
    return 2
}

func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
    if component == 0 {
        return bananas.count
    }
    else {
        let selectedBanana = pickerView.selectedRow(inComponent: 0)
        return fruitArray[banana[selectedBanana]]!.count
    }
}

func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {


    let selectedBanana = pickerView.selectedRow(inComponent: 0)
    let selectedCherry = pickerView.selectedRow(inComponent: 1)


    bananaPicked = bananas[selectedBanana]
    cherryPicked = fruitArray[bananaPicked]![selectedCherry]


    pickerView.reloadAllComponents() 
    }


func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
if component == 0 {
    return bananas[row]
}
else {
    let selectedBanana = pickerView.selectedRow(inComponent: 0)
    return fruitArray[selectedBanana]![row]
}
}

现在，当我(比方说)在 banana2 和 cherry3 中，但我切换到 banana1 时，我得到一个 indexOutOfRange 错误，因为第一个香蕉数组当然没有第三个项目。每当香蕉行更改为将樱桃行重置为 0 时，我都希望如此。

__________ 更新 ____________这是我发现的导致崩溃的另一个错误 (indexOutOfRange)，我发布了一个屏幕截图。

Answer 1

当组件 0 更改时，将组件 1 中的选定行设置为 0。

此外，无需重新加载所有组件。只有组件 1 需要重新加载。

func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {

    if component == 0 {
        pickerView.selectRow(0, inComponent: 1, animated: false)
    }

    let selectedBanana = pickerView.selectedRow(inComponent: 0)
    let selectedCherry = pickerView.selectedRow(inComponent: 1)

    bananaPicked = bananas[selectedBanana]
    cherryPicked = fruitArray[bananaPicked]![selectedCherry]

    //pickerView.reloadAllComponents()
    pickerView.reloadComponent(1)
}

对于第二次崩溃，尝试一些防御性编程来避免崩溃:

func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
    if component == 0 {
        return bananas[row]
    }
    else {
        let selectedBanana = pickerView.selectedRow(inComponent: 0)
        let rowData = fruitArray[bananas[selectedBanana]]!
        if rowData.indices.contains(row) {
            return rowData[row]
        } else {
            return nil
        }
    }
}